Catalytic performance of silica covered bimetallic nickel-iron encapsulated core-shell microspheres for hydrogen production

Supported nickel-iron catalysts with core/shell structures (Ni,Fe/SiO2, and Ni/SiO2, Fe (Imp.)) were synthesized by sol-gel microencapsulation and sol-gel microencapsulation-impregnation methods, respectively. Sol-gel microencapsulation resulted in the formation of Ni and Fe containing alloys, where both Fe and Ni were in the core (Ni,Fe/SiO2). In the case of combined microencapsulation-impregnation Ni was placed in the center where Fe was on the shell side (Ni/SiO2, Fe (Imp.)). BET, XRD, SEM, TGA and Raman Spectroscopy techniques were used for catalysts characterization. Catalysts were tested in dry reforming of methane (DRM) reaction which was specially selected to provide a comprehensive utilization of methane and carbon dioxide. The catalytic activity tests were carried out at 750 degrees C and atmospheric pressure, using stainless steel, temperature-controlled tube reactor. After 3 h of reaction, Ni,Fe/SiO2 bimetallic core-shell microsphere catalysts with Ni/Fe ratio of 4/1 and 2/1 indicated the highest CH4 conversions (74% and 68%, respectively) and H-2/CO (0,72 and 0,69) ratios. Ni,Fe/SiO2 catalysts showed higher activity compared to Ni/SiO2, Fe (Imp.) catalysts and an activity increase for both types of catalysts were observed due to increasing Ni amount in catalyst structure. Ni,Fe/SiO2 catalysts were also determined to be highly resistant against coke formation. A significant resistance against coke formation on active sites was achieved via SiC formation during reaction. The catalyst with best performance (4Ni,1Fe/SiO2) was regenerated after use and tested on following three successive cycles under identical experimental conditions. Results indicated similar activity values with negligible deactivation. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.